Copolyether glycols, i.e., copolymers of alkylene oxides or cyclic acetals with tetrahydrofuran (THF) and end terminated with hydroxyl groups, are well known and useful in the manufacture of polyurethanes. These glycols can be prepared by copolymerizing alkylene oxides or cyclic acetals with THF, using an acid-activated bleaching earth such as montmorillonite clay as a catalyst and water or a polyhydric alcohol as a chain terminator. Such a process is shown in British Pat. No. 854,958.
This method of preparation has not been generally used because the clay particles are quite small and tend to disperse in the reaction medium, and are therefore difficult to separate from the polymer product when the reaction is finished.
It has now been found that copolyether glycols can be prepared by copolymerizing alkylene oxides or cyclic acetals with THF, using
(1) a catalyst which, although more complex than that, can for purposes of summary be described as a polymer containing alphafluorosulfonic acid groups; and PA1 (2) a chain terminator which is water or an alkanediol of 2 to 10 carbon atoms. PA1 P represents the polymer segment of the catalyst; PA1 R is an hydroxyalkyl group of 2 to 10 carbon atoms; and PA1 represents the copolyether chain. PA1 X is hydrogen or an alkyl radical of 1 to 4 carbon atoms. PA1 D is hydrogen, an aliphatic or aromatic hydrocarbon radical of 1 to 10 carbon atoms, a halogen atom or a segment of the polymer chain; PA1 X and Y are hydrogen, an aliphatic or aromatic hydrocarbon radical of 1 to 10 carbon atoms or fluorine, but at least one must be fluorine; PA1 R is a linear or branched linking group having up to 40 carbon atoms in the principal chain, and PA1 Z is hydrogen, an aliphatic or aromatic hydrocarbon radical of 1 to 10 carbon atoms or halogen.
The physical nature of the catalyst and its low solubility in the reaction mass makes it easy to separate from the product at the end of the polymerization reaction and therefore makes the process especially suited for being run in a continuous fashion. The catalyst's low solubility also minimizes catalyst loss as the reaction proceeds.